Transformer for electric discharge lamps



Nov. 29, 1960 c. E. STRECKER TRANSFORMER FOR ELECTRIC DISCHARGE LAMPSFiled May 27, 1959 l l l I l I I l I l l United States PatentTRANSFORMER FOR ELECTRIC DISCHARGE LAMPS Charles E. Strecker, deceased,late of Danville, Ill., by Jeanne E. Strecker, executrix, Danville,Ill", assignor to General Electric Company, a corporation of New YorkFiled May 27, 1959, Ser. No. 816,343

11 Claims. (Cl. 315-97) This invention relates to electric dischargelamps and more particularly to ballast apparatus for starting andoperating such lamps.

It is a characteristic of electric discharge lamps, such as fluorescentlamps, that their internal resistance decreases as the current flowtherethrough increases. It is, therefore, necessary in the installationof such devices to provide means which will limit the current flowthrough the device to a safe value. In addition, it may also bedesirable to provide a higher voltage for initially starting or causinga discharge in the device than is conventienty available. When electricdischarge devices are operated on alternating current, it isconventional practice to provide a single high reactance ballasttransformer to perform these two functions, i.e., limit current andprovide a high initial starting voltage. Such a transformer provides ahigh open circuit voltage for starting and also, by virtue of this highreactance, provides impedance during normal operation to limit thecurrent flow.

A high reactance transformer is one in which the primary and secondarywindings are loosely coupled so that when the transformer is carrying aload, there is a a substantial amount of leakage flux and the voltagesinduced in the windings by this leakage flux cause the transformer tohave a relatively high effective series reactance, or what is commonlyknown as leakage reactance. The conventional way of constructing such atransformer is to arrange the primary and secondary windings ondifferent parts of the core and to provide a magnetic shunt between thewindings thereby providing a path for the leakage flux. This shunt isusually provided with an air gap so calibrated that the operatingcurrent of the secondary coil of the transformer Will be limited to thedesired value. The high, starting voltage can be achieved with a highvoltage secondary winding, or may be achieved by using a transformerwith the primary winding and the operating secondary winding connectedin autotransformer relation, i.e., the primary and secondary areconnected in series across one of the lamps so that their voltages areadditive, as more fully described in my copending application Serial No.816,342, filed on the same date herewith and assigned to the sameassignee as the instant application. However, it is sometimes desirableto produce a higher starting voitage than is available by theutilization of the primary and operating secondary voltages alone. Sucha higher starting voltage may be achieved according to the instantinvention by utilizing the voltage induced in an auxiliary startingsecondary winding across one or more of the lamps during startingthereof.

'When the primary winding and secondary windings are connected inautotransformer relation, it may be desirable that the output voltage bereduced after the device has started; the autotransformer connection atthis point may become unnecessary and, in fact, undesirable. Such atransformer which provides autotransformer type starting voltage in astarting aid circuit and isolated transformer type running voltage ismore fully described in my co- "ice pending application Serial No.435,753, filed June 10, 1954, and assigned-to the same assignee as thepresent invention.

It is, therefore, an object of this invention to provide an improvedballast transformer apparatus for starting and operating electricdischarge lamps which will incorporate the desirable features set forthabove.

A more specific object of this iIlVI1tlOIl is to provide an improvedballast transformer apparatus for starting and operating electricdischarge lamps which will provide a starting voltage across the lampshigher than that available from the primary and operating secondaryopencircuit voltages alone.

Further objects and advantages of this invention will become apparentand the invention will be better understood by reference to thefollowing description and the accompanying drawing, and the features ofnovelty which characterize this invention Will be pointed out withparticularity in the claims annexed to and forming a part of thisspecification.

This invention, in one embodiment thereof, includes a ballasttransformer apparatus having a primary winding, an auxiliary startingsecondary winding, and an operating secondary winding on a magnetic coreand all connected in series in autotransformer relation so that theirvoltages are additive and cooperate to start the lamps. Once the lampshave started, however, since the auxiliary starting winding is in serieswith a low capacity starting capacitor across one of the lamps, only asmall amount of current can flow through this winding and, therefore,the auxiliary starting winding does not form a part of the operating,

circuit. The added voltages of the auxiliary-starting secondary and atleast the operating secondary are, therefore, applied across at leastone lamp during starting thereof. A further feature of the instantinvention is that the additive voltages of the primary, auxiliarystarting secondary and operating secondary are applied between one ofthe lamp cathodes and a conductive part of fixture in a starting aidcircuit. After starting of the lamps, the ballast transformer apparatusmay operate the lamps as an autotransformer or as a substantiallyisolated secondary transformer.

As explained thus far, the circuit has a low power factor since nocorrection has been made. The circuit described above would draw laggingcurrent through the transformer. It may be desirable, but not necessary,to draw leading current through the transformer, as, for example, byhaving a capacitor in series with the operating secondary winding. Or,it may be desirable, but not necessary, to correct the power factor tonear unity as, e.g., by connecting a condenser across a portion of theprimary winding or equivalent winding.

It will be seen that by using the additive voltage of a startingauxiliary secondary, the operating secondary may be made smaller sincethe output voltage during starting therefrom need not be as great. Also,this additive voltage of the auxiliary starting secondary, which becomesundesirable once the lamp is started and is operating, is not effectiveafter starting. It will be readily appreciated that since the auxiliarystarting winding is substantially ineffective after starting of thelamps, it may be wound of relatively fine wire, and may, if desired, beof relatively high impedance thereby further limiting the current flowtherethrough after starting. Since the auxiliary starting winding issubstantially ineffective after starting of the lamps, it may be coupledto either the primary winding or the operating secondary winding.

In the drawing,

Figure 1 is a schematic diagram of an improved ballast transformer foroperating a pair of serially connected discharge lamps according to theinstant invention;

Figure 2 is a schematic diagram of another modification for an improvedballast transformer according to the instant invention for operating apair of serially connected discharge lamps; and,

Figure 3 is a plan view of the ballasting transformer according toFigure 2.

Referring to Figure 1, there is shown a ballasting transformer apparatusaccording to the instant invention for starting and operating a pair ofserially connected discharge lamps. The ballasting apparatus accordingto the instant invention includes a magnetic core 1 having a centralwinding leg 2 and yoke sections 3 and 4 and having a primary winding P,an operating secondary winding 8,, and an auxiliary starting secondarywinding S on the winding leg 2. The primary Winding P is loosely coupledto the operating secondary winding S The primary P and the operatingsecondary winding S may be placed side by side on the central windingleg 2 of the magnetic core 1. thereby resulting in leakage reactance inthe magnetic circuit. Where it is desired to increase the magneticleakage and therefore the leakage reactance of the transformer, this mayreadily be accomplished by the inclusion of high reluctance flux leakagepaths or shunts in the core 1 between the primary P and the operatingsecondary S It will be understood that, depending upon the design of thetransformer, the flux leakage paths may be formed either throughnonmagnetic material such as air, or through magnetic material as by theprovision of the projecting shunt legs 4a formed on the core 1. Thisshunt construction results in what is known as a high reactancetransformer and the transformer acts to limit the current flow in thecircuit including the lamps. This is necessary due to the negativeresistance characteristics of the lamps.

The auxiliary starting secondary winding S may be coupled with one ofthe other windings; as shown in Figures 1 and 3, the starting secondaryS is coupled with the primary P, being wound over it. It will beunderstood, however, that secondary winding S could be placed closelybeside one of the other windings in order to obtain the desiredcoupling.

The primary P has a pair of leads 5, 6 for connection to a source ofalternating current 7, 8. As explained above, the low potential side ofthe normal residential and commercial distribution systems is grounded,as shown at 9. The primary P and operating secondary S are connectedthrough line 10 in autotransformer relation. The other end of theoperating secondary S is connected through leads 11 and 12 in serieswith the auxiliary starting secondary S to form substantially anautotransformer connection therewith. A starting capacitor 13 ofrelatively low capacitance is inserted in series with the auxiliarystarting secondary S between the starting secondary S and the operatingsecondary the purpose of which will hereinafter be explained. A firstcathode heating winding 14, a second cathode heating winding 15, and athird cathode heating winding 16 are also on the magnetic core 1. Asshown, cathode heating winding 16 is an extension winding of the primaryP; it is to be understood, however, that it may be an isolatedsecondary.

The ballasting transformer apparatus is connected to operate a pair ofserially connected discharge lamps L L Lamp L has a pair of electrodes17, 18, one in each end thereof. Lamp L has a pair of electrodes 19, 20,one in each end thereof. The lamps L L are in close proximity to aconducting fixture 21 thereby being in capacitive relation therewith. Asnormally installed, fixture 21 would be grounded through ground 22thereby being in circuit relation with the low potential line 8 of thesupply source (and thereby to the low potential lead 6 of the primary P)through the grounds 9 and 22. However, to insure that the fixture 21 isin fact in electric circuit relation with a low potential line 8 of thesupply source, it may be desirable, but not necessary, to connect thelow potential lead 6 of the primary P to the ballast case 23 through ahigh ohmage resistor 24. The ballast case 23 is normally connected, asshown at 25, to the lamp fixture, thereby securing the fixture inelectrical circuit with the low potential lead 6 of the primary P andthe low potential line 8 of the supply source. A first pair of outputleads 25, 26 connect the cathode heating winding 14 to one electrode 19of lamp L A second pair of output leads 27, 28 connect the cathodeheating winding 15 to electrode 20 of lamp L and electrode 17 of lamp LA third pair of output leads 29, 30 connect the third cathode heatingwinding 16 with electrode 18- of larnpL The low potential lead 6 of theprimary P is connected to one output line 29 connected to the thirdcathode heating winding 15. A series circuit including the auxiliarystarting secondary S and the starting capacitor 13 is connected acrossthe second lamp L in parallel therewith by having one end connected toone output line 25 (through.line 12) connected to thefirst cathodeheating winding 14 and having its other end connected to output lead 28connected to cathodeheating winding 15.

A first starting circuit or loop including lamp L consistsof the seriescircuit including the primary P, the operating secondary S the startingcapacitor 13 (through lines 11, 12), the auxiliary starting secondary Sand the first lamp L As lamp L has not yet started, it is nonconductingand does not form a part of this starting loop. When leads 5 and 6 areconnected across the source of alternating current, the current willflow through the primary P so as to excite the secondaries S and S Theopen circuit voltage resulting in the secondaries S and 5 will be afunction of the number of turns of the secondaries with respect to thenumber of turns of the primary P. Since lamp L is nonconducting, theadditive voltages of the windings are placed across the electrodes 17and 18 of the first lamp L Prior to the starting of the first lamp L arelatively small starting current is flowing, and the starting capacitor13 has no substantial effect upon this starting loop, There will,therefore, be a relatively high voltage applied across the electrodes17, 18 of the first lamp L At the same time, an auxiliary starting aidcircuit or loop includes the additive voltages of the primary P, theoperating secondary S and the starting secondary S applied to electrode17 of the first lamp L which is in capacitive relation with theconducting fixture 21. A return ground with conducting fixture 21 iscompleted through ground 22 to either ground 25 of the ballast case orground 9 of the low potential line 8. Due to the very high impedancethereof, the relatively high voltage applied between electrode 17 of thelamp and the conducting fixture 21 causes a relatively small current topass therebetween. This current will preferably be on the order of a fewmicroamps, which is sufiicient to increase substantially the ionizationof the gas around the electrode 17 and cause the lamp L to becomeconducting, and the current will arc across between electrodes 17 and18.

After the first lamp L has started, a second starting loop includinglamp L will consist of the primary P, the first secondary S and thevoltage existing at the electrode 17 of the first lamp L There willsimultaneously be a relatively high voltage applied between electrode 20and the conducting fixture 21, through ground 22 and ground 25 or ground9. As explained above, the gas in lamp 1.2 will ionize causing lamp L tobecome conductive and the voltage across lamp L issufficient to startthe lamp.

Once lamps L and L have both started, the starting capacitor 13 hassufficient impedance that no significant operating current will flowthrough winding S and the current. through the starting capacitor 13will be minor with reference to the current through the lamp. The lampsL and L will then operate in a series circuit across the primary P andthe operating secondary. S1. Also, after completion of the circuitthrough the lamps,

because of the high impedance of the capacitive coupling of the lampsand fixture, the amount of current flow from the lamp cathodes to theconducting fixture 21 is infinitesimal with relation to the currentthrough the lamps and there is, therefore, only a very minor circuit,from a current standpoint, completed through the grounds. Transformer 1will now, for practical purposes, act as an ordinary high reactanceautotransformer with the combined voltages of the primary P andoperating secondary S producing suflicient current to keep the lamp Land L in operation.

The hallasting transformer of Figure 2 is similar to that illustrated inFigure 1 except that the transformer has its primary and secondarywindings connected to operate the lamps in isolated secondary relationrather than in autotransformer relation, as more fully taught in theabove referenced copending application Serial No. 435,753. A furthermodification illustrated in Figure 2 is the inclusion of a capacitor oflarge capactive reactance in series with the operating secondary S todraw leading current through the lamps. This, of course, is a matter ofdesign and the invention as illustrated in either Figures 1 or 2 may beapplied to either a leading or a lagging circuit.

Referring now to Figure 2, there is illustrated the improved ballastingtransformer according to the instant invention and comp-rising amagnetic core 1 within a case or housing 23. The magnetic core 1 haswound thereon a primary winding P, an operating secondary winding S andan auxiliary starting secondary winding S also wound on the magneticcore 1 are cathode heating windings 14, 15 and 16. A pair of input leads5, 6 are connected to the primary P for connection to a source ofalternating current 7, 8. As hereinafter explained, the low potentialside 8 of the supply source in a normal residential or commercialdistribution system would be grounded as indicated by a ground 9. Such aground, however, is not necessary for the operation of the ballastingtrans former providing the low potential side 6 of the primary P is incircuit relationship with the conducting fixture 21 as hereinafterdescribed. The high potential line 5 connected to the primary P isconnected to one end of the operating secondary S in autotransformerrelation. The line connecting the primary P and the secondary S mayinclude, if desired, a high resistance 31, which will afford certainsafety precautions as more fully described in the above referencedcopending application Serial No. 435,753. It is to be understood,however, that where the safety precautions afforded by resistance 31 arenot needed, resistance 31 may be omitted from the circuit withouteffecting the operation thereof. Serially connected to the operatingsecondary S is a power capacitor 32 of sufficient size relative to theinductance of the transformer to draw leading current through theballasting transformer. It is to be understood, however, that theinstant invention is equally applicable to a lagging circuit, forexample, as described in connection with Figure 1 above, and that in theevent that a lagging circuit is desired, the capacitor 32 may beomitted. The transformer is connected to operate a pair of seriallyconnected discharge lamps L and L The first discharge lamp L has acathode 17 in one end and another cathode 18 at the other end; thesecond discharge lamp L has a first cathode 19 in one end and a secondcathode 20 in the other end.

The lamps L and L are in close proximity to a conducting fixture 21 andare therefore in capacitive relationship therewith. The conductingfixture 21 may be at the same potential as the low potential line 8. Itis customary in normal residential and commercial distribution systemsin this country tohave the low potential side of the input linegrounded. It is also customary that the.

at the primar Windi g-J l'tm ybs. de ir b e b t necessary, to connectthe low potential side 6 of the primary P to the ballast transformercase 23. Since the ballast case is normally mounted on the conductingfixture, this will place the low potential side of the primary windingin circuit with the conducting fixture. It may be desirable, but notnecessary, to place a high ohmage resistor 34 in the circuit connectingthe low potential side 6 with the case 23. Such a circuit through theballast case may be desirable or necessary where the low potential sideof the supply distribution system is not grounded or where the fixtureof the lamp will not normally be grounded, and the high ohmage resistor34 will afford normal safeguards as more fully explained in my abovereferenced copending application Serial No. 435,753.

A first pair of output leads 25, 26 are connected across the firstcathode heating winding 14 for connection across cathode 19 of lamp L asecond pair of leads 27, 28 extend from the second cathode heatingwinding 15 for connection across cathode 20 of lamp L and cathode 17 oflamp L and a third pair of output leads 29, 30 extend from the thirdcathode heating winding 16 for connection across cathode 18 of lamp LThe starting capacitor 13 is in series with the auxiliary startingsecondary S and has sufiicient impedance to limit the current flowtherefrom after the starting of the lamps. The series circuit of theauxiliary starting secondary S and the starting capacitor 13, as shown,has one end connected to one output lead 25 from the first cathodeheating winding 14 (through line 12) and has the other end connected toone output lead 28 from the second cathode heating Winding 15.

An auxiliary starting aid circuit is formed of the series loop includingthe primary P, the high resistance 31, the operating secondary 8,, thepower capacitor 32, through lines 11 and 12 to starting capacitor 13,the auxiliarystarting secondary S through line 28, simultaneously tocathode 17 of lamp L and cathode 20 of lamp L to the conducting fixture21 (which is in capacitive relation with lamps L and L and throughelectrical circuit 33 and resistance 34 to the low potential end 6 ofthe primary P. The additive voltages of the primary winding P and thesecondary windings S and S are applied between cathodes 17 and 20 andfixture 21.

A first lamp starting loop including lamp L is formed of the operatingsecondary 8,, the power capacitor 32 through lines 11 and 12 to thestarting capacitor 13, the auxiliary starting secondary S to cathode 17of lamp L to the other cathode 18 of lamp L With no current flowing, thecombined open circuit voltages of the secondaries S and S are placedacross the lamp L the starting capacitor 13 offers no impedance to theapplication of voltage between electrodes 17 and 18 as no significantcurrent is flowing through this circuit before the lamp L has started.As explained above, when lines 5 and 6 are connected across the sourceof alternating current, the current will flow through the primary P,exciting the secondaries S and S and the lamp L will ignite due to thevoltage of S and S applied across it and due to the ionization in thearea of electrode 17 as a result of the additive voltages of the primaryP and the secondaries S and S applied between the electrode 17 and theconducting fixture 21. p I

Once the first lamp L has ignited, a second starting loop including Lwill be composed of the voltage induced in the operating secondary Sless the voltage across lamp L and capacitor 32. This voltage across theelectrodes of lamp L in connection with the ionization in the area ofelectrode 20 due to the additive voltages of the pricuitbecause, aftercompletion of the circuit across electrodes of lamps L and L the amountof current throughv secondary S becomes minor with reference to thecurrent, in the operating secondary. Likewise, the impedance of resistor31 coupled with the impedance ofiered by the capacitive relation ofelectrodes 17 and 20 to the conducting fixtures 21 is sufllcicnt tolimit the flow of current in this auxiliary starting circuit so that thecurrent flow from the electrodes 17 and 20 to the fixture 21 becomesinfinitesimal with relation to the currentbetwcen the electrodes of therespectivelamps and there is, therefore, only a minor circuit, from atcurrent standpoint, completed to the conducting fixture 21. The lamps Land L therefore, operate in closed circuit with the operating secondaryS and the power capacitor 32 as a substantially isolated secondarytransformer.

It will be understood from the modifications discussed above that theinvention may be advantageously used in many different types of lampcircuits. Therefore, while this invention has been explained bydescribing particular embodiments thereof, it will be apparent thatimprovements and modifications may be made without departing from thescope of the invention as defined in the appended claims.

What is claimed as new and desired to secure by Letters Patent of theUnited States is:

1. Ballast transformer apparatus for starting and op erating at leastone fluorescent lamp and having two spaced electrodes at the respectiveends of said lamp, comprising, a magnetic core having a primary windingand a first secondary winding thereon, output leads for connecting atleast the said secondary winding across the lamp, means providingleakage reactance between said windings, a pair of input lines on saidprimary winding for connection to a source of alternating current, asecond secondary winding on said magnetic core, said windings beingwound and connected in voltage adding relation, and circuit meansincluding a starting capacitor for connecting said second secondarywinding across said lamp in a series starting circuit with at least saidfirst secondary winding, said starting capacitor having sufficientreactance to render said second secondary winding substantiallyineffective after said lamp is started.

2. Ballast transformer apparatus for starting and operating at least onefluorescent lamp mounted near a conductive part and having two spacedelectrodes at the respective ends of said lamp comprising, a magneticcore having a primary winding and a first secondary winding thereonconnected in autotransformer relation, means providing leakage reactancebetween said windings, output leads for connecting at least thesecondary winding across said lamp, a pair of input lines on saidprimary winding for connection to a source of alternating current, asecond secondary winding on said core, said windings being wound andconnected in voltage adding relation. circuit means including a startingcapacitor for connecting said second secondary winding across said lampin a series starting circuit with at least said first secondary winding,and circuit means for connecting the low potential end of said primarywinding in circuit with said conductive part to form a starting aidcircuit thereby to complete an electrical path for said primary windingand said secondary windings during starting, the current through saidstarting aid circuit being minor with reference to the current throughsaid lamp after starting thereof, said starting capacitor havingsufficient reactance to render said second secondary windingsubstantially ineffective after said lamp is started.

3. Ballast transformer apparatus for starting and operating at least onefluorescent lamp mounted near a conductive part and having two spacedelectrodes at the respective ends of said lamp comprising, a magneticcore having a primary winding and a first secondary winding thereonconnected in autotransformcr relation,

means providing leakage reactance-betweensaid wind-- ings, output leadsfor connecting at least the secondary winding across said lamp, a pairof input lines on said primary winding for connection to a source ofalternating current, a second secondary winding on said core, saidwindings being wound and connected in voltage adding relation, andcircuit means for connecting the low potential end of said primarywinding in circuit with said conductive part to form a starting aidcircuit thereby to complete an electrical path for said primary windingand said secondary windings during starting, said circuit meansincluding a starting capacitor for connecting said second secondarywinding across said lamp, the current through said starting aid circuitbeing minor with reference to the current through said lamp afterstarting thereof, said starting capacitor having suflicicnt reactance tosubstantially limit the current flow through said second secondarywinding and said second secondary winding having a relatively highimpedance thereby further limiting the current flow therethrough.

4. Ballast transformer apparatus for starting and operating a pair ofserially connected fluorescent lamps mounted in a conductive fixture andhaving spaced electrodes at their respective ends comprising, a magneticcore having a primary winding and a first secondary winding inductivelycoupled therewith, means providing leakage reactancc between saidwindings, output leads for connecting at least said secondary wind ngacross said pair of seria ly connected lamps, a pair of input lines onsaid primary winding for connection to a source of alternating current,a second secondary winding on said core, said windings being wound andconnected in voltage add ng relation, and circuit means including astarting capacitorfor connecting said second secondary winding acrossone of said lamps in a series starting circuit with at least said firstsecondary winding, said starting capacitor having suflicient reactanceto render said second secondary winding substantially ineffective aftersaid lamp is started.

5. Ballast transformer apparatus for starting and operating a pair ofserially connected fluorescent lamps mounted in a conduct ve fix ure andhaving spaced electrodes at their respective ends comprising, a magneticcore having a primary winding and a first secondary winding thereonconnected in autotransformer relation, means providing leakage reactancebetween said windings, output leads for connecting said windings acrosssaid pair of serially connected lamps, a pair of input lines on saidprimary winding for connection to a source of alternating current, asecond secondary winding on said core, said windings being wound andconnected in voltage adding relation, and circuit means including astarting capacitor for connecting said windings across one of said lampsin a series starting circuit, said starting capacitor having sulficientreactance to render said second secondary winding substantiallyineffective after said lamp is started.

6. Ballast transformer apparatus for starting and operating a pair of seially connected fluorescent lamps mounted in a conductive fixture andhaving spaced electrodes at their respective ends comprising, a magneticcore having a primary winding, a first secondary winding, a secondsecondary winding, 21 first cathode heating winding, a second cathodeheating winding, and a third cathode heating winding thereon. circuitmeans connecting the high potential end of said primary winding and thelow potential end of said first secondary winding in autotransformer reation, means providing leakagereactance between said primary winding andsaid first secondary winding, a first pair of output leads from saidfirst cathode heating winding for connection across one electrode of oneof the lamps, a second pair of output leads from said second cathodeheating winding for connection to the other cathode of said first lampand for connection to one cathode of the second lamp, a third pair ofoutput leads from said third cathode heating wind-- ing for connectionto the other cathode of said second lamp, circuit means for connectingat least the first secondary winding across said pair of seriallyconnected lamps, a pair of input lines on said primary winding forconnection to a source of alternating current, said primary winding andsecondary winding being wound and connected in voltage adding relation,a series circuit including a starting capacitor and said first pair ofoutput leads and having its other end connected to one of said secondpair of output leads whereby a series starting circuit is formed, andmeans for connecting the low voltage end of said primary winding incircuit with said conductive fixture thereby to complete an electricalpath for said primary and secondary winding during starting, saidstarting capacitor having sufficient reactance to render said secondsecondary winding substantially ineffective after said lamps arestarted.

7. Ballast transformer apparatus for starting and operating a pair ofserially connected fluorescent lamps mounted in a conductive fixture andhaving spaced electrodes at their respective ends comprising, a magneticcore having a primary winding and a first secondary winding thereon,circuit means connecting the high potential end of said primary windingand the low potential end of said secondary winding in autotransformerrelation, means providing leakage reactance between said windings,output leads for connecting said windings across said pair of seriallyconnected lamps, a pair of input lines of said primary winding forconnection to a source of alternating current, a second secondarywinding on said core, said windings being wound and connected in voltageadding relation, and circuit means including a starting capacitor forconnecting said second secondary Winding across one of said lamps in aseries starting circuit with said primary winding and first secondarywinding, and means for connecting the low potential end of said primarywinding in circuit with said conductive fixture thereby to complete anelectrical path for said windings during starting, the current throughsaid fixture circuit being minor with reference to the current throughsaid lamps after starting thereof, said starting capacitor havingsufficient reactance to substantially limit the current flow throughsaid second secondary winding and said second secondary winding having arelatively high impedance thereby further limiting the current flowtherethrough.

8. Ballast transformer apparatus for starting and operating a pair ofserially connected fluorescent lamps mounted in a conductive fixture andhaving spaced electrodes at their respective ends comprising, a magneticcore having a primary winding and a first secondary winding thereon,circuit means connecting the high potential end of said primary windingand the low potential end of said secondary winding, means providingleakage reactance between said windings, output leads for connectingsaid secondary winding across said pair of serially connected lamps, apair of input lines on said primary winding for connection to a sourceof alternating current, a second secondary winding on said oore, saidwindings being wound and connected in voltage adding relation, circuitmeans including a starting capacitor for connecting said secondsecondary winding across one of said lamps in a series starting circuitwith said first secondary winding, and means for connecting the lowpotential end of said primary winding in circuit with said conductivefixture thereby to complete an electrical path for said windings duringstarting, the current through said fixture circuit being minor withreference to the current through said lamps after starting thereof.

9. Ballast transformer apparatus according to claim 8 above wherein saidcircuit means for connecting the high potential end of said primarywinding to the low potential end of said secondary winding includes ahigh resistance for isolating said primary winding from the operatingcircuit after said lamps are started.

10. A lighting system comprising, a conductive fixture, at least onefluorescent lamp mounted alongside said fixture, a high reactanceballast transformer comprising a magnetic core having a primary windingand a first secondary winding thereon, circuit means con necting thehigh potential end of said primary winding and the low potential end ofsaid secondary winding in autotransformer relationship, output leadsconnecting said lamp to at least said secondary winding, 21 pair ofinput lines on said primary winding for connection to a source ofalternating current, a second secondary winding on said core, saidwindings being wound and connected in voltage adding relation, andcircuit means including a starting capacitor for connecting said secondsecondary winding across said lamp in a series starting circuit with atleast said first secondary winding, said starting capacitor havingsufi'icient reactance to render said second secondary windingsubstantially ineffective after said lamps are started.

11. A lighting system comprising a conductive fixture, a pair ofserially connected fluorescent lamps mounted alongside said fixture, ahigh reactance ballast transformer comprising a magnetic core having aprimary winding and a first secondary winding thereon, circuit meansconnecting the high potential end of said primary winding and the lowpotential end of said secondary winding in autotransformer relation,output leads for connecting said secondary winding across said pair ofserially connected lamps, a pair of input lines on said primary windingsfor connection to a source of alternating current, a second secondarywinding on said core, said windings being wound and connected in voltageadding relation, and circuit means including a starting capacitor forconnecting said second secondary winding across one of said lamps in aseries starting circuit with said primary and said first secondarywindings, said starting capacitor having sufiicient reactance tosubstantially limit the current flow through said second secondarywinding and said second secondary winding having a relatively highimpedance thereby further limiting said current flow therethrough.

References Cited in the file of this patent UNITED STATES PATENTS2,810,100 Strecker Oct. 15, 1957 2,820,180 Feinberg Jan. 14, 19582,824,242 Cates Feb. 18, 1958 2,861,217 Feinberg Nov. 18, 1958 2,870,378Abrahams Jan. 20, 1959

